Hardy Citrus Atlas

Liqueur

Elongated yellow and orange citrus fruit hanging on branches

Ichangquat 6-7-2

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Ichangquat 6-7-2 (Citrus cavaleriei ‘Ichangquat 6-7-2’) is a remarkable contemporary hybrid obtained by crossing the Ichang papeda (Citrus ichangensis) with a kumquat (Fortunella). The code 6-7-2 refers to the generation and the individual number in the original selection program. Its exceptional hardiness reaches 0°F (−18°C) according to French-language forum observations, making it one of the few citrus with culinary fruit that can be grown in the ground up to USDA zone 7a, including under markedly continental climates. The compact tree reaches 7 to 10 ft (2 to 3 m) with evergreen foliage recalling both the Ichang papeda (typical winged petioles) and the kumquat, and bears a few fine thorns. Its small fruits of 0.5 to 1 oz (15 to 30 g), with thin, sweet, edible skin and tart, fragrant flesh, are eaten whole. Excellent in confectionery, marmalade, and liqueur. Grafted onto Poncirus, viable up to zone 7a.

A young garden citrus tree with visibly trifoliate leaves

Rusk Citrange

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Rusk citrange (Citroncirus ‘Rusk’) is one of the oldest Poncirus hybrids in the world, created in 1897 by Walter T. Swingle at the USDA to combine the extreme hardiness of Poncirus trifoliata with the flavor quality of the Ruby orange. Named in honor of J. M. Rusk, the first U.S. Secretary of Agriculture, it was officially described in 1905. Its exceptional hardiness reaches 1°F (−17°C), making it suitable for in-ground growing up to USDA zone 7a. The vigorous tree reaches 7 to 10 ft (2 to 3 m) with evergreen to semi-deciduous trifoliate foliage. Its small, flattened, dark orange fruits with reddish highlights contain few seeds and have very juicy flesh with a tart, slightly bitter taste, more edible than most citranges. Excellent as juice, jam, and liqueur. Grafted onto Poncirus, perfect for gardens in zones 7 and 7b.

A citrus tree bearing yellow fruit beside a wall

Citrus Taiwanica (Nansho Daidai)

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Citrus taiwanica Nansho-Daidai (Citrus taiwanica Tanaka & Shimada) is the formal botanical classification of the Taiwanese lemon, a plant endemic to Taiwan reported in the Hsinchu and Nanzhuang regions and in the low-elevation forests of the east of the island by the Taiwanese forestry administration. Its hardiness reaches 9°F (−13°C) on the tree, making it suitable for in-ground growing in USDA zones 7b and 8a. The tree reaches 10 to 13 ft (3 to 4 m) with an upright, thorny habit, aromatic evergreen foliage, and highly fragrant white flowers. Its yellow-green fruits at full maturity, medium-sized, with thick, bumpy skin, ripen in winter and hold a very sour, fragrant juice reminiscent of a natural cross between lemon and bitter orange, with unique resinous notes. Traditionally used in Taiwan in cooking, vinegar, marinade, and traditional medicine. Graft onto Poncirus trifoliata, plant against a south wall.

Whole and halved rough-skinned yellow citrus fruit

Corsican Yuzu

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The Corsican Yuzu (Citrus junos ‘Corse’) is a French selection from the INRAE San Giuliano program in Corsica, which has been acclimating and improving the Japanese yuzu since the 1980s. Its hardiness reaches 9°F (−13°C) on the tree and allows it to be grown in the ground in USDA zones 7b and 8a. The tree grows 7 to 13 ft (2 to 4 m) tall with a spreading rounded habit, aromatic evergreen foliage and very fragrant white flowers. Its golden yellow, round, bumpy fruits, with thick, rough skin, ripen in October and November and concentrate authentic yuzu juice with aromas blending mandarin, grapefruit and orange blossom. Very sour and fragrant. Excellent as zest, as juice, in ponzu vinegar and in pastry. A French pride in yuzu acclimatization, to be preferred over imported yuzu. Graft onto Poncirus trifoliata.

An elongated rough orange citrus fruit on a branch

Karna Khatta Lime

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The Karna Khatta lime (Citrus karna) is an old Indian citrus of unknown parentage, almost certainly a natural hybrid, widely used in India as a rootstock. Its hardiness reaches 10°F (−12°C) on the tree, making it suitable for planting in the ground in USDA zone 8a. The tree grows 8 to 10 ft (2.5 to 3 m) tall with an upright, thorny habit, aromatic evergreen foliage and fragrant white flowers. Its medium-sized fruits (2.8 to 4.6 oz, or 80 to 130 g), golden yellow to deep orange with a moderately thick rind, ripen in winter; the dull orange flesh is acidic, with a faint aroma of sour orange. Excellent in Indian cooking (chutney, achar, dhal), in marinades and as juice. Many seeds. A niche variety for collectors of Asian citrus. Graft onto Poncirus trifoliata, south-facing wall.

An unevenly colored yellow-orange citrus fruit hanging on a branch

Striatta ‘Bizzaria’ Bitter Orange

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The Striatta Bitter Orange, also called Bizzaria di Firenze (Citrus aurantium ‘Striata’), is a famous botanical chimera discovered in the 17th century in a Medici garden in Florence. On a single tree it produces variegated fruits (striped orange, yellow, and green) that combine the characteristics of the bitter orange and the citron in varying proportions. Its hardiness reaches 14°F (−10°C) on the tree, with a USDA zone 8a climate benchmark kept in this entry, indicative and to be confirmed for the cultivated material. The tree can reach 10 to 13 ft (3 to 4 m) in the ground with an irregular, thorny habit, foliage sometimes itself variegated green and cream, and very fragrant white blossom in spring. Its exceptional striped fruits, medium-sized, with bumpy skin, ripen in winter. More ornamental than edible, but their candied peel and fragrant juice are prized by collectors. Graft onto Poncirus trifoliata, plant against a south wall. A historic collector’s piece.

A pile of small round green citrus fruit

Beto Sudachi

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The Beto Sudachi (Citrus sudachi ‘Beto’) is a Japanese selection of sudachi, a traditional citrus of Tokushima Prefecture. Its hardiness reaches 10°F (−12°C) on the tree, making it suitable for in-ground growing in USDA zones 7b and 8a, among the hardiest of the edible Japanese citrus. The tree reaches 6.5 to 10 ft (2 to 3 m) with a rounded habit, aromatic evergreen foliage, and fragrant white blossom. Its flat-round fruits, bright green (harvested green) or golden yellow (at full maturity), small (1.5 to 2 in, or 4 to 5 cm), with thin skin, ripen in September and October and hold a very sour juice, fragrant with lime and yuzu notes, without bitterness. Indispensable in Japanese cooking (fish, soba, sauces, seasoning). A few seeds. Graft onto Poncirus trifoliata, plant against a south wall, in well-drained soil.

Yellow citrus fruit hanging from garden branches

Taiwanica Lemon

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The Taiwanica Lemon (Citrus taiwanica), also called Nansho-daidai, is the only true lemon to reach an exceptional hardiness of 5°F (−15°C) on the tree, which makes it suitable for in-ground growing up to USDA zone 7b. Native to the mountains of Taiwan, it was introduced to Japan, where it naturalized in cold regions. The vigorous tree reaches 10 to 13 ft (3 to 4 m) in cultivation according to catalogs, and up to 16 ft (5 m) according to the Bosc catalog, with an upright, thorny habit, aromatic evergreen foliage, and very fragrant white blossom in spring. Its green fruits turning yellow at full maturity, medium-sized, with thick, bumpy skin, ripen in winter with a very sour, fragrant juice suggesting a natural cross between lemon and bitter orange. Tolerates snow on the tree without damage. Excellent for juice, marinades, marmalade, and Asian cooking. Graft onto Poncirus trifoliata, plant against a south-southwest wall.

Rough yellow citrus fruit hanging on leafy branches

Tada Nishiki Yuzu

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The Tada Nishiki Yuzu (Citrus junos ‘Tada Nishiki’) is a historic Japanese yuzu selection with particularly bumpy, aromatic skin, traditionally grown in Kochi Prefecture. Its hardiness reaches 5°F (−15°C) on the tree, making it suitable for in-ground growing in USDA zones 7b and 8a. The tree reaches 10 to 13 ft (3 to 4 m) with a rounded, spreading habit, aromatic evergreen foliage, and very fragrant white blossom. Its golden yellow, round-bumpy fruits (2 to 3 in, or 5 to 7 cm), with thick skin rich in essential oils, ripen in October and November and concentrate a more intense yuzu fragrance than the classic variety, with higher productivity. The very sour juice is exceptional in zest, juice, ponzu vinegar, and niche pastry. Must be grafted onto Poncirus trifoliata to maximize hardiness. Plant against a south-facing wall, in well-drained soil, with generous winter mulch.

A small citrus plant bearing yellow fruit in a nursery pot

Procimequat

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Origin: Procimequat is an extremely rare citrus hybrid, the result of an experimental program led by Eugene May within the […]

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